Phosphate binding with a thiophene-based azamacrocycle in water.

Structural characterization of the phosphate complex with a thiophene-based macrocycle suggests that two dihydrogen phosphates in a dimeric form are encapsulated in the cavity via several hydrogen bonds from NH···O and CH···O interactions. In the lattice framework, the two dimers are linearly hydrogen-bonded to form a tetramer. 1H NMR titrations suggest that the host forms a 1:1 complex with phosphate, showing an association constant of 120 M-1 in D2O at pH = 5.5. The host guest complexation was further confirmed by ESI-MS in a gas phase.